For example, Japanese Utility Model Disclosure No. 63-89181 discloses a device for preventing extraction of a bill contained in a bill validator. In such an anti-extraction device, as shown in FIGS. 18 and 19, a bill is inserted from an inlet 207 into a space between a pair of side walls 202 and 203 on a frame 201, and then carried by belts 211 and rollers 212 between protrusions 209 formed on the frame 201 and protrusions 210 formed on a plate 205. When the bill passes the protrusions 209 and 210, it is slightly deformed however, whose deformation is limited within a range that does not prevent transportation of the bill. If a wrong attempt is made to outwardly withdraw the bill through the inlet 207 by pulling a string such as a fishing line connected to the bill after the bill passes an outlet 208, the engagement of the bill with the protrusions 209 and 210 is effective to inhibit extraction of the bill.
Disclosed in Japanese Utility Model Disclosure No. 7-20790 is an anti-extraction device of another type with a stopper which extends into a passageway of a bill validator, but is mounted rotatably away from the passageway in response to a validating signal of the bill validator. This anti-extraction device is very effective to prevent pulling of the bill since the stopper does not rotate away from the passageway unless a genuine bill is transported toward an outlet.
However, the anti-extraction device of FIGS. 18 and 19 cannot detect any pulling means such as a string or tape connected to the bill. Moreover, it is very difficult to provide the protrusions 209 and 210 of their increased extension length because such long protrusions 209 and 210 would make obstacle to transportation of the bill by belts 211 due to engagement of the bill and the protrusions 209 and 210. Therefore, the prior art bill validator is inconveniently subject to unauthorized extraction of bills by strongly pulling a fishing line connected to the bill. In addition, there would be a fear that bills may be damaged by the protrusions 209 and 210 during the transportation even if they can perfectly bar extraction of bills. Accordingly, unauthorized extraction of bills cannot be detected even by the anti-extraction device disclosed in Japanese Utility Model Disclosure No. 7-20790.